The proposed research aims to purify the Ca 2 ion pumping ATPase from human erythrocyte membranes, to reconstitute this ATPase into phospholipid vesicles, and to utilize the reconstituted ATPase for studies of the mechanism of Ca 2 ion ejection from cells. Aims of the project include study of the composition of the purified ATPase, study of its enzyme kinetics and mechanism and concurrent studies of Ca 2 ion transport and Ca 2 ion dependent ATPase. The project also aims to raise antibodies to the Ca2 ion ATPase. Such antibodies will provide a powerful tool for determining the relationship between this ATPase and other membrane ATPases, such as the Ca 2 ion pumping ATPase from sarcoplasmic reticulum. The antibodies will also be utilized to develop a radioimmunoassay for the Ca2 ion ATPase of erythrocyte membranes; such an assay will be useful for estimating the amount of Ca 2 ion ATPase present in the plasma membranes of other cell types. Finally, it is intended to purify the Ca 2 ion ATPase from other tissues, probably beginning with plasma membranes of brain.